Method for protecting metal parts by means of vapor-phase inhibitors of metal corrosion



United States Patent METHOD FOR PROTECTING METAL PARTS BY MEANS OFVAPOR-PHASE INHIBITORS OF METAL CORROSION Ladislav Cerveny, 47Pristavni, Prague, Czechoslovakia No Drawing. Filed Nov. 29, 1956, Ser.No. 624,956 Claims priority, application Czechoslovakia Dec. 15, 1955 6Claims. 01. 21-25 application for protecting steel products againstatmos-' pheric corrosion during long storage or transport overseas. Thevapor phase inhibitors, when compared with other temporary preservingagents are distinguished by higher efficiency and substantially simplerapplication, which is important from the point of view of economy.

A disadvantage of the hitherto known vapour-phase inhibitors is theirlimitation to specific metals, such as steel, nickel and chromium, whichare passivated in a nitrite medium. Other metals such as copper or brassare not protected by nitrite type inhibitors, which even enhance thecorrosion of zinc, cadmium and magnesium.

Vapour-phase inhibitors suitable for the protection of all metals werenot known heretofore.

The method of the invention provides vapour-phase inhibitors fulfillingall the above requirements.

The inhibitors employed are organic derivates of chromic acid in which achromium anion is combined with a suitable organic component to form acompound whose vapor pressure is sufiicient even at the usualtemperature and pressure. The vapours of these organic chromates aresoluble in water and produce at the sur- 2,978,293 Patented Apr. 4, 1961face of metal articles a medium having protective properties.

Organic derivates of chromic acid with a vapour pressure above 10- mm.Hg/20 C. are particularly suitable such as the neutral chromic acidester oftert-butyl alcohol [(CH3)3C]2CI'O4.

When vapour phase inhibitors are used for the protection of finishedproducts in the course of long storage or transport overseas they offerconsiderable advantages as compared with temporary preserving agents.

Vapour-phase inhibitors according to the invention compare favorablywith the hitherto used inhibitors, such as organic derivates of nitrousacid. Their chief advantage resides in the protection which they affordto all metal articles whether they be made of steel, nonferrous or lightmetals, which has not been possible with the hitherto known inhibitors.

I claim:

1. A method of protecting a metal surface against corrosion, comprisingcontacting the metal surface with an ester of chromic acid in the vaporstate.

2. A method as set forth in claim 1, wherein said ester has a vaporpressure of not less than 10* mm. Hg at 20 C.

3. A method as set forth in claim I, wherein said ester is a watersoluble organic chromate.

4. A method as set forth in claim 1, wherein said ester is a chromicacid ester of a tertiary alcohol.

5. A method as set forth in claim 1, wherein the metal surface isexposed to said ester at ambient temperature and pressure.

6. A method of protecting a metal surface against corrosion, comprisingcontacting the metal surface with the neutral chromic acid ester oftert-butyl alcohol in the vapor state.

References Cited in the file of this patent UNITED STATES PATENTS2,053,024 Dreyfus Sept. 1, 1936 2,294,525 Waugh Sept. 1, 1942 2,582,138Lane Jan. 8, 1952 2,607,744 Viles Aug. 19, 1952 2,629,649 Wachter et a1.Feb. 24, 1953

6. A METHOD OF PROTECTING A METAL SURFACE AGAINST CORROSION, COMPRISINGCONTACTING THE METAL SURFACE WITH THE NEUTRAL CHROMIC ACID ESTER OFTERT-BUTYL ALCOHOL IN THE VAPOR STATE.